How do I make an outdoor cat enclosure for my bored cat?

He used to be an indoor/outdoor cat but became an indoor only cat when I got him. I got him cat trees and used to keep the windows open but he figured out that if he leans on the screens they will pop off. His old owners told me that he loved hunting and would bring home a few dead or inured animals home a week.

I would probably make it out of untreated cedar since it has a natural resistance to rot and insects. Does anybody know where I can get some blueprints?